This invention relates to an electron device, and more particularly to a thin film magnetic head, a magnetic head device and a magnetic recording/reproducing device.
As reading elements currently achieved widespread use for thin film magnetic heads, there have been spin valve film structure elements (referred to herein as xe2x80x9cSV elementxe2x80x9d) using giant magnetoresistive (referred to herein as xe2x80x9cGMRxe2x80x9d) effect films, and tunnel magnetoresistive effective elements (referred to herein as xe2x80x9cTMR elementxe2x80x9d). An active region of the spin valve film structure is of a multilayered film structure including a soft magnetic film (free layer), a non-magnetic film, a ferromagnetic film, and an antiferromagnetic film. On both sides of the active region are passive regions of their respective multilayered film structure through which fed to the active region is sense current which flows in the direction parallel to the film surface of the active region.
In the TMR element, an active region is constructed of a ferromagnetic tunnel effective film of a multilayered structure consisting of a ferromagnetic layer, a non-magnetic layer and a ferromagnetic layer. Above and below the active region are passive regions of a multilayered film structure through which fed to the active region is sense current which flows in the direction perpendicular to the film surface of the active region.
In order to improve the sensitivities of the SV elements and the TMR elements to the external magnetic field, end faces of the multilayered film structures are exposed to the medium-facing surface of a slider. In order to insure high wear resistance, durability, corrosion resistance and insulation property of the exposed end faces and to improve their reliability, the medium-facing surface of the slider is deposited on a covering film such as a diamond-like carbon (referred to herein as xe2x80x9cDLCxe2x80x9d).
In depositing the covering film, the medium-facing surface of the slider is cleaned by means of physical and/or chemical etching and thereafter a covering film is deposited on the cleaned surface to form a stable covering film with high adherence.
Since the SV element and TMR element are constructed of their respective multilayered film structures which are made of different materials, the ionization tendencies of the layers constructing each multilayered structure are different from one another. When cleaned, therefore, the layers of the multilayered film structure are etched by their different etching rates. A layer having a larger etching rate is etched deeply, and a layer having a smaller etching rate is etched shallowly. As a result, the end face of the multilayered film structure is etched in concave-convex shape, so the covering film can not be formed so perfectly as to cover the end face with sufficient adhesive strength. That is, remarkable difference in height occurs throughout end faces of adjacent films, so that coverage of a covering film on the end faces becomes incomplete, which in turn problematically makes insufficient the adherence strength of the covering film to the end faces.
These problems are not limited to the thin film magnetic heads. The same holds true in case of electron devices of various kinds having a multilayered film structure whose end faces are covered by a covering film attached thereto.
It is an object of the invention to provide an electron device which eliminates all the disadvantages of the prior art and which improves adherence strength of a covering film to an end face of a multilayered film structure.
In order to achieve the above objects, the present invention provides three aspects of electron devices. The electron device according to the first aspect of the invention includes a laminated film and a covering film. The laminated film includes a fist layer and a second layer. The first layer is formed of a metal or metal alloy. The second layer is formed of a metal or metal alloy different from that of the first layer and adjoins the first layer.
In an adjacent region between the first and second layers, there is provided a concentration gradient layer containing the metal or met alloy contained in the first layer and the metal or metal alloy contained in the second layer. The covering film covers end faces of the first and second layers.
The first and second layers are fundamentally formed of different metals or metal alloys which are selected from metals or metal alloys fulfilling requirements which are imposed on the electron devices. The metals or metal alloys constituting the first and second layers are different in etching rate in physical and/or chemical etching.
According to the invention, in the adjacent region between the first and second layers is formed a concentration gradient layer containing the metal or metal alloy contained in the first layer and the metal or metal alloy contained in the second layer. With this constitution, when a cleaning is carried out by etching on a surface including the end faces of the first and second layers, the end face of the concentration gradient layer is removed to form a gentle or smooth slope in section by etching correspondingly to the concentration gradient so that the end faces of these layers are etched in smoothly connected surfaces without any indentations.
Therefore, the coverage of the covering film on the end faces of the first and second layers is improved to increase the adherence strength of the covering film to the end faces of the multilayered film structures.
In the electron device according to the second aspect of the invention, a laminated film includes a first layer, a second layer and a third layer. The first layer is formed of a metal or metal alloy, while the third layer is formed of a metal or metal alloy different from that of the first layer. Therefore, the first and third layers exhibit different etching rates in cleaning by etching.
The second layer is arranged between the first and third layers and formed of a mixture of the metal or metal alloy contained in the first layer and the metal or metal alloy contained in the third layer. A covering film covers end faces of the first, second and third layers.
In the electron device according to the second aspect of the invention, the etching rate of the second layer is set to be an intermediate value between those of the fist and third layers so that the coverage of the covering film on the end faces of the first, second and third layers is improved to increase the adherence strength of the covering film to the end faces of these layers.
In an electron device according to the third aspect of the invention, a laminated film includes a first layer, a second layer and a third layer. The first layer is formed of a metal or metal alloy, while the third layer is formed of a metal or metal alloy different from that of the first layer. Consequently, the first and third layers exhibit different etching rates in cleaning by physical and for chemical etching.
The second layer is aged between the first and third layers and formed of a metal or metal alloy having an etching rate intermediate between the etching rate of a metal element whose atomic ratio is more than 40% of the first layer and whose atomic number is the maximum and the etching rate of a metal element whose atomic ratio is more than 40% of the third layer and whose atomic number is the maximum. A covering film covers end faces of the first, second and third layers.
According to the third aspect of the invention, it is possible to set the etching rate of the second layer substantially intermediate between those of the first and third layers, so that the coverage of the covering film on the end faces of the first, second and third layers is enhanced to increase the adherence strength of die covering film to the end faces of these layers.
Moreover, herein are disclosed thin film magnetic beads as practically applied examples of the first, second and third aspects of the invention, a magnetic head device as a combination of the thin film magnetic head with a head supporting device, and a magnetic recording/reproducing device as a combination of the magnetic head device with a magnetic recording medium such as a magnetic disc according to the invention.
As can be seen from the above description the present invention can provide an electron device having a covering film covering multiple film end faces, whose adherence strength to the end faces is improved.
Other and further features and advantages of the invention will be explained in more detail with reference to attached drawings illustrating preferred embodiments of the invention which are not intended to limit the invention.